The invention relates to a method of manufacturing an object having a surface structure, the method employing pressure members which are movable relative to one another and which have facing pressure surfaces by which a first element and a second element, which has a relief on a surface, are pressed against one another to provide the second element with a microstructure by cold deformation.
Such a method can be used for manufacturing an optical medium, in particular a disc-shaped information carrier provided with one or more circular or spiral optically readable tracks. The first element may then be a master disc which can be used directly as a stamper. Such a stamper comprises a planar plastics substrate having an embossed information surface comprising raised portions (bumps) formed in an expansion layer and representing information bits. A retention layer overlies the expansion layer. When the method is carried out the stamper is positioned opposite a basic structure (second element) comprising an optically transparent plastics substrate with a non-cured or incompletely cured layer carrying a light-reflecting layer, generally of a metal. By means of pressure members the stamper is pressed against the basic structure to transfer the information present in the information-carrying surface of the stamper to the incompletely cured layer. Pressing may proceed until the incompletely cured layer has been cured by means of UV radiation. The pressure member acting against the stamper is made of steel and the pressure member supporting the basic structure is made of a UV-transmitting quartz.
A drawback of the method described above is that when the first and the second element are pressed against one another differences in radial extension between the elements and pressure members which are in contact with one another occur and depending on the prevailing friction give rise to shear stresses and/or stick-slip effects at the contact surfaces between the elements and the pressure members, thereby distorting the information during the information transfer.